Intraperitoneal alpha-radioimmunotherapy in mice using different specific activities

Area of Science:

• Oncology
• Radiochemistry
• Immunotherapy

Background:

• Ovarian cancer remains a significant health challenge, necessitating novel therapeutic strategies.
• Alpha-radioimmunotherapy offers a targeted approach to cancer treatment.
• The monoclonal antibody MX35 F(ab")(2) targets ovarian cancer cells.

Purpose of the Study:

• To evaluate the therapeutic efficacy of alpha-radioimmunotherapy for ovarian cancer in a mouse model.
• To investigate the impact of varying specific activities of 211At-MX35 F(ab")(2) on treatment outcomes.

Main Methods:

• Ovarian cancer cells (NIH:OVCAR-3) were inoculated into mice.
• Groups of mice received 211At-MX35 F(ab")(2) at different specific activities (130, 65, 32, 16, or 4 kBq/microg).
• Control groups received unlabeled MX35 F(ab")(2). Tumor and ascites presence was assessed 8 weeks post-treatment.

Main Results:

• Tumor-free fractions (TFFs) varied across specific activity groups.
• A specific activity of 4 kBq/microg resulted in a significantly lower TFF (0.17) compared to 130 kBq/microg (0.67).
• No tumor-free animals were observed in the unlabeled antibody control group.

Conclusions:

• Therapeutic efficacy of 211At-MX35 F(ab")(2) was dependent on specific activity.
• Specific activities between 130 and 16 kBq/microg did not show a significant difference in outcome.
• Lowering specific activity to 4 kBq/microg markedly reduced the therapeutic efficacy.